1. Technical Field
The present invention concerns a metal cylinder head gasket.
2. Related Art
In the case of engines with inserted cylinder liners, local depressions often occur in the area of the pressure limiter due to high temperatures. Conventionally inserted cylinder head gaskets cannot conform to the profile of these depressions and fill the resulting gaps. This causes wear and results in leaks between the sealing surfaces of the cylinder head and engine block.
From JP 08178070 a cylinder head gasket is already known that has a functional plate featuring an additional half bead in the area facing the combustion chamber, or that has a second functional plate on the inner side of the first functional plate, serving to prevent the emergence of additional stresses when a gap arises between the cylinder head and the lining. However such a cylinder head gasket is not able to satisfy the requirements for flexibility and sealing ability at the same time.
It is the task of the present invention, therefore, to develop the known cylinder head gasket from the state of the art, in such a way that it is able to fill gaps arising from local depressions in the area of the pressure limiter, in particular in the case of engines with cylinder linings.
This is achieved by locating a pressure limiter for a full bead on a first functional plate on the side of the latter that faces a second functional plate, and by locating a plate having an elastic element in or on the second functional plate in the plane of the pressure limiter. The elastic element extends in the vertical plane of the pressure limiter. The elastic element increases the surface pressure in such a way that there is a sufficient sealing pressure at any given time because the elastic element of the second functional plate makes it possible for the cylinder head gasket to conform, with permanent elasticity, to the profile of the depressions in the cylinder lining.
Preferably, the pressure limiter is a ring insert that is preferably joined to the first functional plate by welding in such a way that they are gas-tight in relation to one another. This is optimally achieved by spot-welding the ring insert to the first functional plate.
The elastic element preferably comprises a half bead. Half beads are preferable to full beads for spatial reasons, i.e., due to space requirements, and also due to their specific surface pressure. A half bead presses against the adjacent plate on each side over one of the two contact areas so as to provide essentially the same specific surface pressure, in the installed position, over both of the cylinder head gasket""s two contact areasxe2x80x94whereas in the case of a full bead, which presses against adjacent plates over one contact area on one side and over two contact areas on the other side, the specific surface pressure on one side is only half as great as on the other side.
According to a preferred embodiment, the plate with the half bead is joined to the second functional plate as one piece, so that material is saved and failure-prone or defect-prone areas are obviated because there are no weld seams and the like.
In a preferred embodiment, the area bordering the half bead is planar. The sealing pressure is thus further increased. The pressure limiter is preferably also planar.
In the installed position, the elastic element is supported on the cylinder lining in order to achieve as high an elasticity as possible and thus as high a compensation as possible of uneven stresses as well as an improved sealing in this area.
Furthermore, at least one more bearing plate can be positioned either between the first and second functional plates or below the second functional plate. By using additional plates, the surface pressure and sealing ability can be controlled and varied.